Hi Martijn, I am Paulo and I'd like to help.
If you have a browser open, maybe it is hijacking the media keys that's why it doesn't work on Spotify and VLC. Try to close them and see if it works.
If not, try to set it to disable on your browsers and see if it would make a difference.
Enter this if you have Chrome:
chrome://flags/#hardware-media-key-handling
If you have Edge:
edge://flags/#hardware-media-key-handling
If still not working, try the following
Close all apps before performing the below steps.
- Press the Windows key + R, type Services.msc and hit Enter.
- Then, locate for Human Interface Device Service from the list and look for the status of this service whether the service is started or stopped.
- If the service is stopped, then click on the Human Interface Device Service and click on Start.
- If the service is already started, then click on Restart to restart the service.
- Relaunch the Spotify/VLC and see if the media key would work